The present invention relates to a process and an apparatus for freezing liquid or semiliquid foods in the form of essentially uniform pellets.
Liquid or semiliquid food products are frequently frozen in block form for subsequent thawing and consumption by catering services and individual households. The disadvantages of this form of freezing are many, for example the quality suffers from the long freezing and thawing times, the user objects to it because optional portioning is not possible, and the fact that the product must be packaged prior to freezing increases the cost. In contrast hereto, the freezing of liquid or semiliquid food products in particulate form, i.e. in the form of powders, granules, pellets or the like, brings several advantages. In this manner, rapid freezing and also rapid thawing is made possible, which is advantageous from the viewpoint of quality. Freezing in particle form enables the producer to simplify packaging in portions of different sizes, while the consumer is able to thaw merely the food quantity he requires at the moment.
Among prior art processes for the freezing liquid and semiliquid food products in particulate form is the process of disposing the product on a cold surface, planar or cylindrical, on which the product is partially or completely frozen, whereupon it is scraped from the surface and sorted according to size prior to packaging, or is formed by compression or extrusion to the desired form prior to packaging. This process suffers from the disadvantage that it is not very gentle toward the product which, if it contains solid particles, may deteriorate both during the scraping and the compression or extrusion.
Another process for freezing liquid or semiliquid food products in particulate form comprises freezing the food in a bath of carbon dioxide snow. By mixing the food with the carbon dioxide snow, the food is made to form granules. The granules resulting from this process are of different sizes, for which reason sorting must be effected prior to packaging. Granules which are too small can be recycled to the process. However, also this process suffers from the disadvantage that it is not sufficiently gentle toward liquid products containing solid particles. Furthermore, it is not possible to obtain uniform particles, and some variation of both the particle size and the particle form must be accepted.
Another process for freezing said food products in particulate form implies freezing the food in containers of desired shape and volume and expelling the food from the containers after freezing. This process is complicated from the viewpoint of production engineering and also suffers from the disadvantage that it is difficult to prevent the product from freezing fast in the containers.
Still another process for freezing the said food products in particulate form includes spreading the product on a conveyor belt which may be planar, corrugated or provided with recesses of a desired shape. The product spread on the belt is conducted thereon through a freezing zone and, after passing through said zone, is separated from the belt. If the belt is formed with recesses, this process has essentially the same shortcomings as the preceding one. If a planar or corrugated belt is used, the product which is rod-shaped or stratified after freezing, must be divided. At least for some products, such treatment is undesirable and, besides, always is accompanied by product waste. Finally, the belt freezing process is unsuitable for products which, in the frozen state, adhere to the belt and thus are difficult to detach therefrom.